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Trials within cohorts （TwiCs） are design methods derived from randomized controlled trials （RCTS）. They have been widely used in chronic disease areas such as tumors and cardiovascular diseases. The basis of the TwiCs design is a prospective cohort of specific diseases. When RCTS need to be implemented， some patients meeting the inclusion and exclusion criteria are randomly sampled from the cohort to receive "trial interventions"， while the remaining patients in the cohort who meet the inclusion and exclusion criteria continue to receive conventional treatment as control groups. By comparing the efficacy differences between the intervention measures of the trial group and the control group， the efficacy of intervention measures was evaluated. Within the cohort， the same process could be repeated to carry out multiple RCTS， so as to evaluate different intervention measures or compare the efficacy of different doses or timing of interventions. Compared with classical RCTS， TwiCs make it easier to recruit patients from the cohort and have higher external validity， providing a new research paradigm for improving the efficiency and applicability of RCTS in clinical practice. However， TwiCs may also face the challenge of poor compliance of patients in the cohort. Researchers need to take effective measures to control these patients in the design and operation of TwiCs. This article focused on the methodological key points during the implementation of TwiCs， including multi-stage informed consent （patients are informed of consent at three stages： entering the cohort， entering the trial group， and after the trial）， randomization procedures （only random sampling of patients from the cohort to receive "trial interventions"）， sample size calculation， and statistical analysis methods. The article also compared the differences between TwiCs and traditional RCTS and illustrated TwiCs research design and analysis with examples， so as to provide new research ideas and methods for clinical researchers.
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Wuzhuyu Decoction, the classical formula recorded in the Treatise on Febrile Diseases(Shang Han Lun), has been included in the Catalogue of Ancient Classic Prescriptions(the First Batch). Consisting of Euodiae Fructus, Ginseng Radix et Rhizoma, Zingiberis Rhizoma Recens, and Jujubae Fructus, it is effective in warming the middle, tonifying deficiency, dispelling cold, and descending adverse Qi, and is widely applied clinically with remarkable efficacies. For a classical formula, the chemical composition is the material basis and an important premise for quantity value transfer. This study aimed to establish a rapid identification method of chemical components in Wuzhuyu Decoction by high-resolution mass spectrometry(HR-MS) and molecular network. AQUITY UPLC BEH C_(18) column(2.1 mm×100 mm, 1.7 μm) was used for sample separation, and acetonitrile-0.1% formic acid in water was used as mobile phases for gradient elution. Q-Exactive Orbitrap MS data were collected in positive and negative ion modes, and GNPS molecular network was plotted according to the similarity of MS/MS fragmentation modes. Cytoscape 3.6.1 was used to screen molecular clusters with similar structures. Finally, the chemical components of Wuzhuyu Decoction were rapidly identified according to the controls, as well as the information of retention time, accurate relative molecular weight of HR-MS, and MS/MS multistage fragments. A total of 105 chemical components were identified in Wuzhuyu Decoction. This study can provide data for the follow-up quality control, standard substance research, and pharmacodynamic material research on Wuzhuyu Decoction, as well as references for the rapid qualitative analysis of the chemical components of Chinese medicine.
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Tandem Mass Spectrometry/methods , Chromatography, High Pressure Liquid/methods , Drugs, Chinese Herbal/chemistry , Quality ControlABSTRACT
Objective To analyze the risk factors of preoperative lymph node staging (N-stage) deficiency in gastric cancer and establish a preoperative assessment model to assist in predicting preoperative N-stage. Methods A retrospective method was used to analyze the clinicopathological data of 268 patients with gastric cancer. The patients routinely underwent preoperative thin-section enhanced CT to assess preoperative N-stage. Results The risk factors for preoperative N-stage deficiency were analyzed in combination with postoperative pathological findings. Multifactorial logistic regression analysis was performed to determine influencing factors, and Kaplan-Meier analysis was used to plot the survival curves of preoperative N-stage accurate group and deficiency group. The nomogram plot and ROC curves of the prediction model were drawn using the R package. AUC, 95%CI, sensitivity, and specificity were calculated. Results Age, BMI, poor differentiation, and Lauren's classification as diffuse were independent risk factors for preoperative N-stage deficiency in gastric cancer (P < 0.05). Prognostic survival was significantly worse in the preoperative N stage-inadequate group than that in the accurate group (P=0.041). The AUC area was 0.935, with a sensitivity of 85.9% and specificity of 96.9%. Conclusion Young age, high BMI, poor differentiation, and Lauren's classification as diffuse are independent risk factors for preoperative N-stage deficiency. The established preoperative assessment model based on age, BMI, differentiation degree, and Lauren's classification in this study has relatively high credibility.
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Objective To analyze the clinical nursing effect of multi-stage health education in patients after vitreoretinal microscopy and its effects on their knowledge mastery and the adverse events. Methods The clinical data of 100 patients who had received vitreoretinal microsurgery between April 2015 and April 2017 were analyzed. These patients were divided into 2 groups by random digits table method.The 50 cases given routine nursing were taken as the control group,whereas the other 50 given both routine nursing and multi-stage health education as the observation group.The clinical nursing effect, knowledge mastery and adverse events were compared between the two groups. Results The position holding time and the length of hospital stay was respectively(171.45±25.36)min and(8.10±1.05)d in the observation group,and was respectively(90.20±24.10)min and(10.40±2.31)d in the control group,with the difference between the two groups being statistically significant (t =16.422, 6.409, P<0.05). The percentages of relevant skills and knowledge mastery was respectively 92.00% (46/50) and 96.00% (48/50) in the observation group, and was respectively 60.00% (30/50) and 64.00% (32/50) in the control group,with statistically significant difference shown between the two groups(χ2=14.035,16.000,P<0.05). Patients with increased intraocular pressure, impaired vision and sore eyes in the observation group accounted for 24.00% (12/50), 26.00% (13/50) and 26.00% (13/50) respectively, whereas those with increased intraocular pressure,impaired vision and sore eyes in the control group was respectively 82.00%(41/50),80.00%(40/50)and 86.00%(43/50),the difference was significant(χ2=33.762,29.265,36.560,P<0.05). Conclusions For patients who had undergone vitreoretinal microsurgery, multi-stage health education can prolong the duration of position holding,shorten the length of hospital stay,and improve the patients'knowledge mastery and reduce the incidence of adverse events.
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Objective To explore the sampling method in China National Human Biomonitoring Program (HBP) and the related errors,so as to calculate and evaluate the study design in sampling.Methods The sampling method of HBP is of multistage nature.Taking the results of sampling method from Guizhou province as an example,results related to sampling error and variation coefficient were calculated,using the multistage unequal probability sampling error method.Results The HBP covered 152 monitoring sites in 31 provinces (autonomous regions and municipalities) and with 21 888 residents selected.The replacement rates at various stages were 5.26％,6.35％ and 40.6％ respectively.The sampling error in Guizhou province was 3 207 594,and the coefficient of variation was 0.097.Conclusions According to the multi-stage unequal probability sampling method,the sampling coefficient variability appeared small with high precision,in Guizhou province.However,this method did not consider the weight adjustment of non-sampling errors such as population missing rate and response rate.Methods related to the calculation on multi-stage sampling error among large-scale public health monitoring projects need to be further studied.
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Objective To explore the sampling method in China National Human Biomonitoring Program (HBP) and the related errors,so as to calculate and evaluate the study design in sampling.Methods The sampling method of HBP is of multistage nature.Taking the results of sampling method from Guizhou province as an example,results related to sampling error and variation coefficient were calculated,using the multistage unequal probability sampling error method.Results The HBP covered 152 monitoring sites in 31 provinces (autonomous regions and municipalities) and with 21 888 residents selected.The replacement rates at various stages were 5.26％,6.35％ and 40.6％ respectively.The sampling error in Guizhou province was 3 207 594,and the coefficient of variation was 0.097.Conclusions According to the multi-stage unequal probability sampling method,the sampling coefficient variability appeared small with high precision,in Guizhou province.However,this method did not consider the weight adjustment of non-sampling errors such as population missing rate and response rate.Methods related to the calculation on multi-stage sampling error among large-scale public health monitoring projects need to be further studied.
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This study was aimed to optimize the extraction process of Aesculi. The extraction process of Aesculi wasoptimized through orthogonal experiment while the transfer rate of escin Ia and escin Ib. And the yield of dry extract. wasadopted as marks. And ratio of solid to liquid, the ethanol concentration, extraction time and extraction temperature werestudies. The results showed that optimized extraction conditions of Aesculi were determined as follows. The ratio of solidto liquid was 1: 10, the ethanol concentration was 70％, extracted for 20 minutes ever stage and the extractiontemperature was 60℃. It was concluded that the extraction process is efficacious for general flavone and icariinextraction. The method is suitable for the standardized production technology of Aesculi.
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OBJECTIVE@#To explore the effect of immunogenicity and immunizing protection of GAMA gene DNA vaccine, which was related with merozoite, ookinete and sporozoite invasion.@*METHODS@#Gene fragments were obtained using PCR technique and eukaryotic expression vector (containing immunostimulatory sequence) was built. BALB/c mice were divided into PBS control group, empty vector control group and study group and were immunized at week 0, 3 and 6 respectively. Blood was collected 2 weeks after each immunization and serum was separated to detect the IgG, IgG1 and IgG2a levels. Spleen of mice was obtained for preparation of splenic mononuclear cell and the cytokine IL-4 and IFN-γ levels were detected. Indirect immunofluorescence and western blot were employed to verify the specificity of antiserum. Sporozoite and merozoite invasion were used respectively to detect the immune protective effect 2 weeks after the third immunization. Ookinete conversion rate in vitro and oocyst numbers of mosquito stomach were observed to evaluate the transmission-blocking levels.@*RESULTS@#In GAMA DNA vaccine group: antiserum could be combined with recombinant protein specifically and green fluorescence signals of merozoite, ookinete and sporozoite were observable, while specific fragments and fluorescence signals were not observable in empty vector group. Compared with control group, specific IgG in DNA vaccine immunity group significantly increased (P < 0.01), and IgG1 and IgG2a all increased (P < 0.01). IL-4, IFN-γ content in study group significantly increased, compared with control group (P < 0.01). GAMA DNA vaccine immunity could not obviously block the erythrocyte-stage infection (caused by sporozoite invasion); compared with control group, liver worm load was slightly reduced (P < 0.05), and antiserum ookinete numbers (cultured in vitro) had no significant difference with oocyst numbers of mosquito stomach in DNA vaccine group.@*CONCLUSIONS@#GAMA has good antigenicity, which could stimulate the body to produce specific immune responses; while DNA vaccine immunity could not play a good protective effect, the effect of which is only limited to the slight reduction of liver worm load, and has no obvious erythrocyte-stage protective effect and transmission-blocking effect. Therefore, trying other immunization strategies for further research on the value of GAMA (as multi-stage antigen vaccine and multi-stage combined vaccine components of the life-cycle of plasmodium) is necessary.
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Multistage sampling is a frequently-used method in random sampling survey in public health.Clustering or independence between observations often exists in the sampling,often called complex sample,generated by multistage sampling.Sampling error may be underestimated and the probability of type Ⅰ error may be increased if the multistage sample design was not taken into considerationin analysis.As variance (error) estimator in complex sample is often complicated,statistical software usually adopt ultimate cluster variance estimate (UCVE) to approximate the estimation,which simply assume that the sample comes from one-stage sampling.However,with increased sampling fraction of primary sampling unit,contribution from subsequent sampling stages is no more trivial,and the ultimate cluster variance estimate may,therefore,lead to invalid variance estimation.This paper summarize a method of variance estimation considering multistage sampling design.The performances are compared with UCVE and the method considering multistage sampling design by simulating random sampling under different sampling schemes using real world data.Simulation showed that as primary sampling unit (PSU) sampling fraction increased,UCVE tended to generate increasingly biased estimation,whereas accurate estimates were obtained by using the method considering multistage sampling design.
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Objective: To explore the effect of immunogenicity and immunizing protection of GAMA gene DNA vaccine, which was related with merozoite, ookinete and sporozoite invasion. Methods: Gene fragments were obtained using PCR technique and eukaryotic expression vector (containing immunostimulatory sequence) was built. BALB/c mice were divided into PBS control group, empty vector control group and study group and were immunized at week 0, 3 and 6 respectively. Blood was collected 2 weeks after each immunization and serum was separated to detect the IgG, IgG1 and IgG2a levels. Spleen of mice was obtained for preparation of splenic mononuclear cell and the cytokine IL-4 and IFN-γ levels were detected. Indirect immunofluorescence and western blot were employed to verify the specificity of antiserum. Sporozoite and merozoite invasion were used respectively to detect the immune protective effect 2 weeks after the third immunization. Ookinete conversion rate in vitro and oocyst numbers of mosquito stomach were observed to evaluate the transmission-blocking levels. Results: In GAMA DNA vaccine group: antiserum could be combined with recombinant protein specifically and green fluorescence signals of merozoite, ookinete and sporozoite were observable, while specific fragments and fluorescence signals were not observable in empty vector group. Compared with control group, specific IgG in DNA vaccine immunity group significantly increased (P < 0.01), and IgG1 and IgG2a all increased (P < 0.01). IL-4, IFN-γ content in study group significantly increased, compared with control group (P < 0.01). GAMA DNA vaccine immunity could not obviously block the erythrocyte-stage infection (caused by sporozoite invasion); compared with control group, liver worm load was slightly reduced (P < 0.05), and antiserum ookinete numbers (cultured in vitro) had no significant difference with oocyst numbers of mosquito stomach in DNA vaccine group. Conclusions: GAMA has good antigenicity, which could stimulate the body to produce specific immune responses; while DNA vaccine immunity could not play a good protective effect, the effect of which is only limited to the slight reduction of liver worm load, and has no obvious erythrocyte-stage protective effect and transmission-blocking effect. Therefore, trying other immunization strategies for further research on the value of GAMA (as multi-stage antigen vaccine and multi-stage combined vaccine components of the life-cycle of plasmodium) is necessary.
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This study analyzed WHO-standardized nutritional indicators of children from selected households within communities that were sampled from all districts of Botswana. Data from the 2007 Botswana Family Health Survey were fitted into multilevel models that seek to account for variability due to the macro- and micro-units that have been hierarchically selected. This allowed for estimation of different levels of intraclass correlations while simultaneously assessing the model-fit by accounting for the influence on the nutritional indicators due to the fixed variables attributable to these macro- and micro-units. The results show that variation in nutritional status of under-five children in Botswana is a function of characteristics of the households and communities within which they live. As much as 17% of variation is due to differences in the communities and households. Economic status of households holds an important key in predicting the nutritional status of children.
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Background: Aim of current study was to determine the prevalence of obesity in both sexes in persons aged 18-45 years. Methods: Multistage and multiphasic sampling technique was utilized in this study to screen the obese subjects of both males and females based on WHO classification of obesity according to BMI of 18-45 years of age. Each household was visited and only the subjects having age of 18-45 years were included in this study and this comprised of 5107 subjects, then identified obese cases with the help of height and weight techniques. Only those people who had simple obesity were included in the study. People having secondary obesity, drug induced obesity and pregnant ladies were excluded from this study. The data was collected and analysed using statistical software and chi square and proportional statistical test were applied. Results: Out of 5107 screened population, 2652 were males and 2455 were females and the prevalence of male obesity in study population is 6.41% and that of females is 7.74%. Conclusion: The sex has a significant impact on obesity. We reported in our study a prevalence of obesity is more in females as compared to males. A lack of physical activity as well as low frequency of employment makes females more susceptible to obesity.
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Background & objectives: Physicians’ satisfaction/dissatisfaction from their job is an important factor associated with health service that deals with human life. This study was conducted to ascertain overall level and proportion of physicians’ satisfaction from their job as well as to identify those components that influenced it. Method: A comprehensive customized questionnaire was used with Section A to assess demographic profile of physicians and Section B to assess satisfaction. Response to each question was devised using Likert scale. Likert scale responses were converted to normal scale so that statistical procedures could be naturally developed. A total of 170 physicians were selected using multistage sampling. Questionnaire was administered on one to one basis to avoid non-response. Precise and contextualized descriptive and inferential statistical procedures were used for analysis. Result: Of the 140 physicians, 103 (74%) were satisfied from their job with average score of 19.15 ± 11.46 while 37 (26%) were dissatisfied with average score -09.27 ± 06.30. Nine out of 15 components were found significant (P<0.05). Conclusion: Comparative assessment of the present results with those of other studies revealed that satisfaction percentage of Indian physicians and those of the developed countries were almost the same. Perhaps, magnitude of satisfaction level (average score) of the Indian physicians were towards the lower side. Nine determinants, identified in this study can be used safely to assess any professionals’ satisfaction.
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Background: Today, tobacco use causes 1 in 10 deaths among adults worldwide – more than five million people a year. By 2030, unless urgent action is taken, tobacco’s annual death toll will rise to more than eight million. Material & method: A community based cross sectional study was undertaken in district Dehradun. Multistage stratified random sampling was done for selection of study area. A sample of 632 was taken for study purpose. Kish method was used for selection of respondents in selected household. Statistical analysis: Chi-square test, Mantel Haenszel Odds Ratio and Multi Variate Logistic Regression Analysis was done to develop results. Significant level was assumed at p<0.05. Results: The overall prevalence of ever use of tobacco was 24.4%. It was more (32.9%) in rural area as compare to urban area (15.8%). Tobacco use was directly proportional to age, more prevalent in Muslims and was indirectly proportional to education & socioeconomic status. Conclusion: Legislation pertaining to tobacco and alcohol sale and use does exist. However its strict enforcement is required in order to reduce the menace.
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OBJECTIVES: The inherent nature of the Korean National Health and Nutrition Examination Survey (KNHANES) design requires special analysis by incorporating sample weights, stratification, and clustering not used in ordinary statistical procedures. METHODS: This study investigated the proportion of research papers that have used an appropriate statistical methodology out of the research papers analyzing the KNHANES cited in the PubMed online system from 2007 to 2012. We also compared differences in mean and regression estimates between the ordinary statistical data analyses without sampling weight and design-based data analyses using the KNHANES 2008 to 2010. RESULTS: Of the 247 research articles cited in PubMed, only 19.8% of all articles used survey design analysis, compared with 80.2% of articles that used ordinary statistical analysis, treating KNHANES data as if it were collected using a simple random sampling method. Means and standard errors differed between the ordinary statistical data analyses and design-based analyses, and the standard errors in the design-based analyses tended to be larger than those in the ordinary statistical data analyses. CONCLUSIONS: Ignoring complex survey design can result in biased estimates and overstated significance levels. Sample weights, stratification, and clustering of the design must be incorporated into analyses to ensure the development of appropriate estimates and standard errors of these estimates.
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Adult , Aged , Female , Humans , Male , Middle Aged , Blood Pressure , Bone Density , Cadmium/blood , Creatinine/blood , Hemoglobins/analysis , Lead/blood , Mercury/blood , Nutrition Surveys , PubMed , Republic of Korea , Research DesignABSTRACT
Objectives: The objective of the study was to determine the level of dental health care access and associated factors, at various public health facilities in the Union Territory (UT) of Chandigarh. Materials and Methods: A study was done using a multistage random sampling technique, to interview adult respondents at their homes and to interview the dentists in the public dental clinics and hospitals. Results: The mean composite access score was 59.2 (SD 18.9) in urban areas and 60.5 (SD 20.9) in rural areas (P=0.64) on a scale of 100. The mean score for the self-perceived condition of their oral health was 6.47 (95% CI 6.17 - 6.76). Thirty-four percent of the respondents did not contact a dentist despite having a problem in the last year, primarily because dental problems were not important for them (45%), they lacked time (22%), and took self-medication (16%). Overall 58% of the respondents suggested government clinics and 44% liked private dentists for treatment of dental cavities. The government setup was preferred because the facilities were cheaper and affordable. Conclusions: Dental health care access and only limited dental facilities were available in most of the dental clinics in Chandigarh. Self-reported dental problem was low, and people ignored their dental problems.
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Adult , Attitude to Health , Community Health Centers , Cross-Sectional Studies , Dental Care/economics , Dental Care/statistics & numerical data , Dental Clinics , Dental Service, Hospital , Educational Status , Female , Health Care Costs , Health Knowledge, Attitudes, Practice , Health Services Accessibility , Hospitals, Public , Humans , India , Interviews as Topic , Male , Middle Aged , Oral Health , Patient Acceptance of Health Care , Primary Health Care , Private Practice , Rural Health Services , Self Report , Urban Health ServicesABSTRACT
The extraction of phytase produced by solid-state fermentation of citrus peel was studied employing a multistage leaching process. It was observed that the extracts containing EDTA retained over 90 percent of phytase activity at room temperature after 24 h after the leaching. A fractional design 2² (with 4 replicates at the central point) was carried out for testing the pH and agitation as process independent factors. Only the interaction between the pH and agitation showed a significant influence. These factors were optimized with a central composite design. Agitation at 300 rpm and pH at 5.0 were the best conditions to extract the enzyme from solid matrix. The modeling of the process indicated that diffusivity of the enzyme in the solvent was the controlling mechanism. The corresponding kinetic constant and saturation concentration in this process were 0.89 min-1 and 4.0 IU/mL, respectively. The multistage process indicated that after two steps, it was possible to recover 85 percent of total enzyme produced.
A extração de fitases produzidas por fermentação em estado sólido de polpa cítrica foi estudada utilizando um processo de extração sólido-líquido em varias etapas. A adição de EDTA permite manter durante 24 horas a temperatura ambiente 90 por cento da atividade inicial do caldo com a enzima extraída. Um planejamento fatorial 2², com 4 replicas no ponto central, foi desenvolvido para testar os valores de ph e agitação convenientes para a extração das enzimas. A interação entre ambos os fatores foi estadisticamente significativa. A atividade da enzima foi otimizada nos valores onde o pH (5.0) e a agitação (350 rpm) resultaram ser as melhores condições para extrair a enzima da matriz sólida. O ajuste do modelo matemático obtido mostra que é possível considerar a difusividade como o mecanismo que controla o processo de transferência de massa. A constante cinética que descreve este processo e a concentração de saturação foram 0.039 min-1 e 4.01 IU/mL respectivamente. A extração em varias etapas mostrou que nas duas primeiras etapas é possível recuperar 85 por cento da fitase produzida.
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O pós-tratamento de efluentes de reatores anaeróbios é um processo necessário para o atendimento dos padrões de emissão. Os resultados aqui apresentados mostram a viabilidade de uso de uma nova configuração de biofiltro aeróbio submerso (BAS) no pós-tratamento desses efluentes. Os BAS multiestágio apresentam uma câmara anaeróbia (V=12,6L), seguido de uma câmara aeróbia (V=30L) e uma câmara anóxica (V=26,4L), todas em série (V total=70L). Neste estudo, foi analisada a remoção de sólidos suspensos (SS), DQO e DBO5. Foram utilizados três BAS multi-estágio preenchidos com três diferentes materiais-suporte: tampas e gargalos PET (165m²/m³), pedra britada n. 4 (50m²/m³) e anéis Pall 1,5'' (135m²/m³). Os reatores foram operados com valores de tempos de detenção hidráulicas (TDH) de 4,1, 8,2 e 12,3 horas, e três taxas de aplicação superficial (TAS) (21, 12 e 8m³/m².d). A associação dos reatores UASB+BAS possibilitou remoções de DQO total superiores a 90 por cento para os BAS 1 e 3, e 85 por cento para o BAS 2, sendo independente do TDH aplicado. A remoção de SS foi maior no BAS contendo anéis Pall, provavelmente devido ao maior índice de vazios desse material.
The post-treatment of effluents from anaerobic reactors is normally a mandatory step to meet the emission standards. The results presented here show the feasibility of using a new configuration of biological aerated filter (BAF) in the post-treatment of UASB reactors. The multi-stage BAF presents an anaerobic chamber (V=12.6L), followed by an aerobic chamber (V=30L) and an anoxic chamber (V=26.4L), all in series (total V=70L). This study examined the removal of suspended solids (SS), COD and BOD5. Three multi-stage BAF filled with three different packing materials were used: lids and bottlenecks of PET bottles (165m²/m³), gravel n. 4 (50m²/m³) and Pall rings 1.5'' (135m²/m³). The reactors were operated with the values of hydraulic detention time (HDT) of 4.1, 8.2 and 12.3 hours, and three superficial application rates (21, 12 and 8m³/m².d). COD removal efficiencies of 90 percent for BAF 1 and 3, and 85 percent for BAF 2 were obtained, being the removal independent of the HDT applied to BAF. The removal of SS was higher in BAF containing Pall rings, probably due to the higher voidage of this material.
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Multistage sampling techniques are widely applied in the cross-sectional study of epidemiology, while methods based on independent assumption are still used to analyze such complex survey data. This paper aims to introduce the application of weighted estimation methods for the complex survey data. A brief overview of basic theory is described, and then a practical analysis is illustrated to apply to the weighted estimation algorithm in a stratified two-stage clustered sampling data. For multistage sampling survey data, weighted estimation method can be used to obtain unbiased point estimation and more reasonable variance estimation, and so make proper statistical inference by correcting the clustering, stratification and unequal probability effects.
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A pesquisa apresenta uma avaliação do sistema de Filtração em Múltiplas Etapas (FiME), utilizando instalação piloto composta por duas unidades de pré-filtros dinâmicos em série, três linhas de pré-filtros de escoamento ascendente, em série e em camadas, e quatro filtros lentos com diferentes meios filtrantes. O desempenho do sistema foi avaliado através de parâmetros como turbidez, cor aparente, sólidos suspensos, coliformes totais e fecais e ferro. Os resultados mostraram que as três linhas de pré-filtros de escoamento ascendente apresentaram comportamento semelhante em todas as carreiras de filtração. Os quatro filtros lentos tiveram igual desempenho com relação a sólidos suspensos e os filtros lentos 3 e 4 alcançaram as maiores remoções de ferro, turbidez e cor em algumas carreiras de filtração.
This work presents an evaluation of some alternatives of multistage filtration system (MSF), using a pilot plant comprising two dynamic roughing filters, in series, three lines of upflow roughing filters, linked in series and in layers and four slow sand filters with different granular media composition. The performance of the system was evaluated by monitoring some water quality parameters such as: turbidity, suspended solids, total coliforms, fecal coliforms and particle size. The results showed that the MSF system produced effluents with low turbidity, solids and coliforms. The three lines of upflow roughing filters indicated the same efficiency in all tests. The four slow sand filters had similar performance concerning solids reductions and the slow sand filters 3 and 4 reached the greatest reductions in iron, organic matter, turbidity and color, in some experiments.